Conductor wrapping bit and method for forming a surface thereon

ABSTRACT

A rotary bit for wrapping conductor wire about a terminal in helical convolutions to form an electrical connection. The bit includes a longitudinal terminal-receiving bore and a conductor wire-receiving groove in radially offset parallelism therewith. A wire-camming surface slopes radially inwardly from the transverse end face of the bit to the terminal bore and includes a helical rise for continuously camming and supporting a major portion of successive wire convolutions. A wire guide surface intersects the conductor groove and sloped camming surface for feeding the wire into camming position. The sloped camming surface is formed by a rotary form machining tool which is simultaneously rotated relative to the bit longitudinal axis and axially moved relative to the bit end face.

[limited States Patent 72] Inventors William J. Baker Reed City; RichardJ. Hurst, Hersey, both of Mich. [211 Appl. No. 828,822 [22] Filed May29, 1969 [45] Patented Dec. 7, 1971 [73] Assignee Gardner-Denver CompanyQuincy, Ill.-

[54] CONDUCTOR WRAPPING BIT AND METHOD FOR FORMING A SURFACE TIl-IEREON4 Claims, 8 Drawing Figs.

242/7.17, 29/203 [51] lint. Cl B2lf3/02, B2lf 15/00 [50] Field of Search29/203 H, 203 DT;140/117,118,119,122,124;242/7.17, 7.06

[56] References Cited UNITED STATES PATENTS 2,758,797 8/1956 Miklau242/7.l7 3,078,052 2/1963 Olds et a1 242/7.l7

Primary Crammer-Charles W. Lanham Assistant Examiner-E. M, CombsAtlorney-Michael E. Martin ABSTRACT: A rotary bit for wrapping conductorwire about a terminal in helical convolutions to form an electricalconnection. The bit includes a longitudinal terminal-receiving bore anda conductor wire-receiving groove in radially offset parallelismtherewith. A wire-camming surface slopes radially inwardly from thetransverse end face of the bit to the terminal bore and includes ahelical rise for continuously camming and supporting a major portion ofsuccessive wire convolutions. A wire guide surface intersects theconductor groove and sloped camming surface for feeding the wire intocamming position. The sloped camming surface is formed by a rotary formmachining tool which is simultaneously rotated relative to the bitlongitudinal axis and axially moved relative to the bit end face.

PATENTED 05c 71971 $625262 SHEET 2 UP 2 1 3a 66 at39 BACKGROUND OF THEINVENTION Conductonwrapping tools commonly incorporate a bit which isconnected with a rotary motor and joumaled in a surrounding stationarysleeve. The bit is usually provided with a longitudinal bore forreceiving an electrical terminal and a radially offset groove forreceiving a stripped end portion of a wire which is to be wound inhelical convolutions about the terminal upon rotation of the bit.

Known conductor-wrapping bits include types having surfaces opening tothe end face of the bit which operate to cam portions of the conductorwire radially inwardly onto the terminal as the winding process iscarried out. This camming action enhances the electrical and mechanicalintegrity of the connection in various ways. Conductor-wrapping bitsknown in the art which have sloped camming surfaces are disclosed inU.S. Pat. No. 2,758,797 to E. P. Miklau and U.S. Pat. No. 3,078,052 toW. L. Olds et al. The conductor-wrapping bit of Miklau provides ahelical sloped surface for camming the end portion of the wire, and thewrapping bit of Olds provides a sloped surface for radial and axialcamming of portions of each wire convolution as well as the end portion.

A longstanding problem in the art of conductor-wrapping bits has beenthe provision of a bit which will compensate for dimensional variationsof the terminal and wire to provide the proper amount of camming actionto assure consistency of the mechanical and electrical characteristicsof connections. The criticality of providing the structural essentialsfor a satisfactory wrapped electrical connection is discussed in detailin U.S. Pat. No. 2,759,166 to R. F. Mallina.

Another problem in the art of wrapping bit design is the provision ofadequate contact area between the bit surface and the conductor so thatwear producing unit pressures between the bit surface and the conductormay be held within reasonable limits. This problem has beensubstantially solved with the improved wrapping bit disclosed in U.S.Pat. No. 3,531,056 issued to applicants on Sept. 29, 1970. Ser. No.683,631 filed by applicants on Nov. 16, 1967. However, the wrapping bitdisclosed in Ser. No. 683,631 does not compensate for dimensionalvariations encountered in mass produced terminals and conductor wire.

SUMMARY OF THE INVENTION In accordance with the present invention thereis provided a conductor-wrapping bit which operates to wrap a conductorwire in successive helical convolutions about a terminal withconsistency of mechanical and electrical characteristics regardless ofdimensional variations which are normally encountered in mass producedterminals and wire. The present invention further provides a wrappingbit having a wire camming and support surface which operates to cam amajor portion of a wire convolution radially inwardly with respect tothe bit axis of rotation and axially forwardly away from the bit endface to assure a properly wrapped connection. By engaging and supportinga major portion of a wire convolution, unit pressure between the bit andwire is reduced; and, accordingly, lateral deflection of the terminal isreduced.

The functional advantages of the present invention are realized in thewrapping operation by a wrapping bit having a camming surface whichsubstantially surrounds the terminal receiving bore and slopes radiallyinwardly from the transverse end face of the bit to theterminal-receiving bore whereby the wire is cammed onto the terminalover a major portion of each convolution regardless of dimensionalvariations in terminal and wire cross section. Furthermore, the bitcamming surface is provided with a helical rise conforming substantiallyto the natural helix of a wire convolution to provide for reducedcontact stress between the bit surface and the wire and to provideuniform camming action. The present invention further includes a wireguide surface intersecting the conductor receiving groove and the slopedcamming surface which is operable to feed the wire into the mostdesirable camming position between the terminal edge and the bit cammingsurface.

The present invention also provides a novel method for forming a helicalsloped surface on a conductor-wrapping bit by simultaneously providingrelative axial movement between the bit and a form machining tool androtating the tool relative to the bit about the longitudinal axis of thelatter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a side elevation, partly insection, of a rotary tool which includes a wrapping bit in accordancewith the present invention.

FIG. 2 is a transverse end view of the conductor-wrapping bit of thepresent invention.

FIG. 3 is a section view taken along the line 3-3 of FIG. 2.

FIG. 4 is a longitudinal section view taken along the line 4- 4 of FIG.2 with a terminal in position and illustrating how the helical-cammingsurface supports a wire convolution.

FIG. 5 is a partial longitudinal section view of the wrapping bitillustrating how the wire-camming surface compensates for variations interminal dimensions.

FIG. 6 is a transverse end view of the wrapping bit in the process ofwrapping a conductor wire about a square terminal.

FIG. 7 is a section view taken along the line 7-7 of FIG. 6.

FIG. 8 is a section view taken along the line 8-8 of FIG. 2 and showinga form machining tool in position to form the bit camming surface.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention isoperable to be used in a variety of tools commonly used in the art ofmaking solderless wrapped electrical connections including hand-heldtools and automatic machines. A typical hand-held or portable conductorwire wrapping tool is illustrated in FIG. 1 and generally designated bythe numeral 10. The tool 10 includes a casing 12 and a handle 14. Thecasing 12 houses a suitable motor which is operated by depressing theoperator trigger 16. The forward end of the tool comprises a sleeve 18attached to the front of the casing 12 and secured thereto by a nut 20.The sleeve 18 includes a stationary collet and nut assembly 22 which isoperable to removably secure an elongated tubular sleeve element 24. Thetubular sleeve 24 is operable to axially retain and rotatably journal aconductor wrapping bit 26 preferably made of heat treatable steel andhaving a bit end face 28 opening to the distal end of the sleeve 24. Thebit 26 includes an integral shank 30 having a portion nonrotatablyengaged with a rotatable spindle 32 by means of a transverse pin 34. Thespindle 32 is suitably rotatably driven by the tool motor whereby thebit 26 is rotated within the stationary supporting sleeve 24. In amanner well known, the conductor wire wrapping bit 26 is operable totightly wrap the stripped end of a flexible electrical conductor wireabout a metallic post or terminal in a series of helical convolutions toform a solderless electrical connection. The particular geometry of thebit end face and surfaces in proximity thereto which comprise animprovement in the art of wire-wrapping bits is set forth herein.

Referring to FIG. 2, a central cylindrical bore 36 opens to thetransverse end face 28 of the bit 26 and is operable to receive asubstantially square cross section terminal 38 (see FIG. 6) in placetherein. The bore 36 extends a sufficient depth into the bit 26 toreceive enough length of the terminal to wrap a plurality ofconvolutions of conductor wire thereon as will be described. Disposedabout the bore 36 and intersecting the bit end face 28' is a conductorwire camming and support surface 40 which slopes radially inwardly withrespect to the longitudinal bit axis 42 from the end face 28 to theintersection with the terminal-receiving bore 36. As viewed in FIG. 2,the surface 40 is formed to have a helical advance in a clockwisedirection around the bore 36. That is, a point at a constant radius fromthe longitudinal axis 42 of the bit 26 and lying on the surface 40 wouldfollow a helical path with respect to said axis if rotated in aclockwise manner.

Also opening to the end face 28 is a conductor wire receiving groove 44comprising a rectangular slot 46 longitudinally formed near thecircumference of the bit and closed by the inner wall 48 of thestationary support sleeve 24 (FIG. 6). An enlarged circular counterboreportion 50 of the wire-receiving groove 44 (see FIG. 7) is provided forreceiving a portion of conductor wire insulation if it is desired toform a wrapped connection having an insulated portion.

Referring to FIGS. 2 and 3, the bit 26 is further provided withwireguiding surface means 52 intersecting the wirecamming surface 40 andthe wire-receiving groove 44. The guiding surface 52 slopes axially withrespect to the longitudinal bit axis 42 (FIG. 3) from the intersectionwith the camming surface 40 to the groove 44. As may be seen in FIG. 3the intersection of the surface 52 with the groove 44 is formed by aradius R over which a conductor wire is bent as it moves from the groove44 along the surface 52 and into the camming position at 54 on thecamming surface 40. As shown in FIGS. 2 and 3 the guide surface 52 isgenerally funnelshaped converging from the intersection with the groove44 to the intersection with the camming surface 40. The longitudinalaxis of the funnel-shaped surface 52 corresponds to the line 33 and liesin a plane parallel to the longitudinal axis 42 of the bit. A preferredmethod of forming the guide surface 52 is by means of a rotary formmilling cutter. Surrounding the conductor wire receiving groove 44 is asomewhat U-shaped recess 58 which is formed to facilitate a coiningoperation which forms the radius R.

As previously mentioned, the operation of a conductor wire wrapping bitis for the purpose of forming a series of contiguous convolutions ofwire wrapped tightly on a terminal. Superior wrapped connections areperformed by bits which cam the wire onto the terminal rather thanmerely pulling the wire around the terminal. Referring to FIGS. 6 and 7.the views show the terminal 38 wrapped with approximately two turns orconvolutions of conductor wire C. However, in commencing a wrappingoperation, the stripped end portion 60 of the conductor wire is insertedin the groove 44 and the wire is laid in the notch 62 in the stationarysleeve 24, see FIG. 6. Usually the insulated portion 64 of the wire Cextends just inside the notch as shown. The tool is then positioned overthe terminal 38 with the terminal extending into the bore 36 as shown inFIG. 7. With wire C held stationary relative to the sleeve 24 at thenotch 62, the tool is operated to rotate the bit 26 in the direction ofthe arrow in FIG. 6. At the beginning of the wrapping operation theconductor wire is pulled out of the groove 44 and guided by thefunnel-shaped guide surface 52 to a position between the camming surface40 and the corner 66 of the terminal 38, see FIG. 6, whereby the wire iscammed by the surface 40 into contact with the terminal. As shown inFIG. 6, there is actually penetration of the terminal corner 66 into thewire C to assure adequate electrical contact area and a gastightconnection. Continued rotation of the bit 26 causes successive portionsof the camming surface 40 to come into camming and supporting contactwith the wire C to wrap a series of helical convolutions.

A distinct advantage of the bit 26 is the provision ofthe helicallysloped camming and support surface 40 which compressively embraces amajor portion of a wire convolution whereby the wire is continuously andsubstantially evenly pressed radially inward against the terminal 38 andaxially against the previous convolution to provide a connection ofsuperior mechanical and electrical character. As can be seen in FIG. 4,by providing a helical advance or lead to the camming surface 40substantially corresponding to the natural lead of a wire convolution 68the camming surface provides continuous and even force against the wireas indicated by the force vectors 70 shown with their axial and radialcomponents. By providing support over a major portion of the peripheryof a wire convolution there is virtually no tendency for thelongitudinal bit axis 42 to wobble relative to the terminal 38 and henceno tendency to bend or deflect the terminal. This reduction ofunbalanced lateral forces between the bit and terminal is enhanced bythe coincident position of the terminal receiving bore axis and the bitrotation axis 42.

A principal advantage of the bit 26 over known conductor wire wrappingbits is illustrated in FIG. 5. The sloping cam surface 40 is operable tocompensate for terminal diagonal dimensional variations which affect theradial location of the terminal corners 66. Ifan undersize or lowerdimensional limit terminal is encountered, the conductor wire C isguided by the funnel-shaped surface 52 onto the camming surface deeperin the recess formed by the surface 40 or further away from thetransverse end face 28 whereby it is properly cammed onto the edge 66.If a terminal 39, designated by the dashed line, having the larger ormaximum diagonal dimension is encountered the conductor, represented bythe dashed circle, comes into camming position on the surface 40 closerto the transverse end face 28. Compensation for dimensional tolerancesin wire diameter is also provided by the geometry of the cam surface 40.Not only does the sloping cam surface 40 compensate for wire andterminal dimensional variations, but the guide surface 52 provides forguiding the wire onto the camming surface at various positions bypermitting the wire to leave the funnel-shaped surface at either a deepor shallow point with respect to the convergence of the surface 52 withthe camming surface 40.

The bit 26 is particularly advantageously used with wire diameter of0.010 inches or less wherein terminals have diagonal dimensions of 0.030inches or less. Tolerances encountered in manufacturing terminals andconductor wire with these minuscule dimensions become a significantportion of the total dimension, and it may be appreciated from theforegoing that a bit in accordance with the present invention operatesto compensate for the imperfections of mass produced terminals and wire.

As previously mentioned, the bit-camming surface 40 slopes radiallyinwardly from intersection with the transverse end face 28 tointersection with the longitudinal terminal-receiving bore 36 and thesurface 40 also has a helical rise with respect to the longitudinal bitaxis 42. Referring to FIG. 8. a preferred method of forming the surface40 is by means of a rotary form machining tool 76. The tool 76 may be amilling cutter or a grinding tool or any suitable tool on which a formsurface 78 may be provided. The tool 76 is rotatable about an axis 80and is rotatably driven by the shank portion 82 which is operative to bedriven by a drive spindle, not shown.

In the operation of forming the surface 40 on the bit 26, the tool 76 ispositioned with its rotative axis 80 a predetermined radial distance rfrom the bit longitudinal axis 42 and parallel thereto. The tool 76 isthen moved relatively toward the bit to penetrate the end face 28 andform the deepest portion of the surface 40, which is at the intersectionof the surface 40 with the funnel-shaped guide surface 52, see FIG. 2.With the tool 76 rotating about its axis 80, simultaneously, and at aconstant rate, the tool is rotated about the axis 42 with the axis 80 asthe radial distance r and axially is moved with respect to the end face28 to form the surface 40 having a helical lead corresponding to thenatural lead of a wire convolution. Reversely, the bit may be orbitedaround the axis 80 of the tool and moved axially with respect to thetool-machining surface 78 to form the surface 40 the result in eitherprocess being to effect relative motion between the bit and the toolwhich will generate the sloped helical surface.

What is claimed is:

l. A bit for wrapping a wire about a terminal in helical convolutionscomprising:

a. a bit end face;

b. a terminal-receiving bore in said end face;

c. a wire-receiving groove opening to said end face;

d. a helically sloped wire camming surface disposed about saidterminal-receiving bore; and,

e. surface means intersecting said wire-receiving groove and saidwire-camming surface and sloping axially with respect to thelongitudinal axis of said bit from said intersection with saidwire-camming surface to said intersection with said wire receivinggroove, said surface means including a substantially funnel-shapedsection converging from said intersection with said wire-receivinggroove to said intersection with said wire-comming surface; for guidingsaid wire into a position for camming said wire onto said terminal bysaid wire-camming surface.

2. The invention set forth in claim 1 wherein:

the longitudinal axis of said funnel-shaped section lies in a planeparallel to the longitudinal axis of said bit.

3. In a bit for wrapping a wire about a terminal in helicalconvolutions:

a. a bit end face;

b. a terminal-receiving bore in said end face;

c. a wire-receiving groove opening to said end face; and,

d. a wire camming and support surface disposed about saidterminal-receiving bore and sloping radially inwardly with respect tothe longitudinal axis of said bit, said camming and support surfacehaving a helical lead corresponding substantially to the lead of a wireconvolution for compressively embracing a major portion of the peripheryof a wire convolution and pressing said wire convolution radiallyagainst said terminal. 4. A bit for wrapping a wire about a terminal inhelical convolutions comprising:

a. a bit end face;

b. a terminal-receiving bore in said end face;

c. a wire-receiving groove opening to said end face;

d. surface means on said bit for camming said wire onto said terminal;and, i

e. wire guide surface means intersecting said wire-receiving groove andsloping axially toward said bit end face for guiding said wire into aposition for camming said wire onto said terminal by said wire-cammingsurface means. said wire guide surface means comprising a substantiallyfunnel-shaped portion converging from said intersection with saidwire-receiving groove toward said bit end face.

t lit 1 I? l

1. A bit for wrapping a wire about a terminal in helical convolutionscomprising: a. a bit end face; b. a terminal-receiving bore in said endface; c. a wire-receiving groove opening to said end face; d. ahelically sloped wire camming surface disposed about saidterminal-receiving bore; and, e. surface means intersecting saidwire-receiving groove and said wire-camming surface and sloping axiallywith respect to the longitudinal axis of said bit from said intersectionwith said wire-camming surface to said intersection with said wirereceiving groove, said surface means including a substantiallyfunnel-shaped section converging from said intersection with saidwire-receiving groove to said intersection with said wirecommingsurface; for guiding said wire into a position for camming said wireonto said terminal by said wire-camming surface.
 2. The invention setforth in claim 1 wherein: the longitudinal axis of said funnel-shapedsection lies in a plane parallel to the longitudinal axis of said bit.3. In a bit for wrapping a wire about a terminal in helicalconvolutions: a. a bit end face; b. a terminal-receiving bore in saidend face; c. a wire-receiving groove opening to said end face; and, d. awire camming and support surface disposed about said terminal-receivingbore and sloping radially inwardly with respect to the longitudinal axisof said bit, said camming and support surface having a helical leadcorresponding substantially to the lead of a wire convolution forcompressively embracing a major portion of the periphery of a wireconvolution and pressing said wire convolution radially against saidterminal.
 4. A bit for wrapping a wire about a terminal in helicalconvolutions comprising: a. a bit end face; b. a terminal-receiving borein said end face; c. a wire-receiving groove opening to said end face;d. surface means on said bit for camming said wire onto said terminal;and, e. wire guide surface means intersecting said wire-receiving grooveand sloping axially toward said bit end face for guiding said wire intoa position for camming said wire onto said terminal by said wire-cammingsurface means, said wire guide surface Means comprising a substantiallyfunnel-shaped portion converging from said intersection with saidwire-receiving groove toward said bit end face.